1. Field of the Invention
This invention relates to a method and apparatus for determining whether a person is capable of performing specific tasks, and more particularly, whether a person is fit to operate a motor vehicle.
2. Description of Related Art
There is a continuing need to increase the density of vehicles traveling the world's roadways, and simultaneously to improve the safety of highway vehicle operations by preventing highway vehicles from colliding with stationary and moving objects (such as roadside obstacles and other vehicles). One means for accomplishing these seemingly contradictory goals is to monitor the relative speed, direction of travel, and distance between vehicles sharing the roadway, and to use such information to provide direct indications to the vehicle's operator of potential danger. It is becoming increasingly more common for automotive engineers to consider the use of microwave radar systems as a means to monitor and warn drivers of such environmental conditions. Another means for accomplishing these diverse goals is to ensure that the driver of each vehicle is fit to operate the vehicle for which the driver is responsible.
Whenever a person is responsible for operating a motor vehicle, it is critical that the person be capable of demonstrating basic cognitive and motor skills at a level that will assure the safe operation of the vehicle. A number of conditions can impair a person's ability to perform the basic cognitive and motor skills that are necessary for the safe operation of a motor vehicle. For example, consumption of alcohol or narcotic drugs, or lack of sleep can make it impossible for a person to react appropriately to a potentially hazardous situation with sufficient speed to avoid danger to the operator, the vehicle, and other people and property which might be in the potential zone of danger. Therefore, it is very important to continuously evaluate a driver's ability to identify an appropriate action and react under the conditions encountered while operating a motor vehicle. Such conditions can cause a driver to experience extreme boredom and fatigue. For example, a truck driver carrying a load of merchandise cross-country is likely to experience boredom and fatigue under the conditions of such a long and monotonous interstate highway trip.
A number of pre-trip tests have been developed which allow a driver's fitness to operate a motor vehicle to be evaluated before the driver enters the vehicle. In one such test, a potential driver is requested to stand or sit before a panel that simulates the dashboard of a vehicle which the potential driver is to operate. A screen, such as a cathode ray tube (CRT) screen, simulates the view the driver would have when looking out the windshield of the vehicle. A mock steering wheel, brake pedal, and accelerator pedal are monitored to detect the reactions of the potential driver to events displayed on the screen. The potential driver's reactions are evaluated to determine whether the potential driver is performing adequately to safely operate a vehicle. The problem with such a pre-trip test is that the driver is only tested at the outset of his shift and it is quite possible for his fitness to deteriorate dramatically in the hours following his pre-trip test.
In a variation of the pre-trip test described above, a potential driver enters a specially-equipped vehicle and pulls down a screen located in the sun visor. Images are displayed on the screen and the driver must react to the images using the actual vehicle controls, such as the brake pedal, the accelerator pedal, and the steering wheel. As is the case in the previously described test, the driver's performance is evaluated by comparing the drivers remeasured reactions to a predetermined standard to determine whether the driver is fit to safely operate the vehicle. Only if the potential driver performs adequately will the engine of the vehicle operate. While this test more closely approximates the conditions encountered by the driver on the road, it nonetheless is not performed under actual conditions or in real-time. Furthermore, the condition of the driver may change during the course of the trip. For example, the driver may consume alcohol or a narcotic drug, or may become sleepy after operating the vehicle for a period of time. Thus, a need exists for dynamic, continuous, real-time testing of a driver's ability to safely operate a vehicle.
Turning the reader's attention now to vehicle borne radar systems as another means for enhancing the safe operation of vehicles, a number of vehicle borne radar systems which monitor the relationship of the vehicle to other vehicles and to obstacles are known. For example, systems are known that transmit and receive at three different frequencies on a time division basis, with two of the frequencies being used to determine range, and the third being combined with one of the first two to determine closing speed and likelihood of collision, are presently known. One such system is disclosed in U.S. Pat. No. 3,952,303 to Watanabe et al., which teaches an analog radar signal processing front end.
However, analog systems such as the one disclosed in Watanabe are sensitive to temperature changes, difficult to calibrate, limited in resolution and reliability, and are require complex processing. Furthermore, such systems are dedicated to particular tasks, such as determining the range and relative rate of motion of other objects, and therefore are difficult to upgrade and customize to meet varying requirements. Still further, the transmit and receive frames in such three frequency systems can be wasteful, in that only small portions thereof are needed to determine the range and relative rate of motion of a target, with the remaining portions of the frame being unused.
Another recent example of an automotive radar system that uses analog signal processing techniques to analyze reflected radar signals is described in U.S. patent application Ser. No. 08/020,600, entitled "Multi-Frequency Automotive Radar System", and assigned to the assignee of the present invention. In that system, a transmit signal and the reflected received signal are coupled to an RF mixer. The relevant output from the RF mixer is a signal that has a frequency equal to the difference between the transmit and receive frequencies. The frequency of the reflected received signal may be shifted from the frequency of the transmit signal upon its return due to the "Doppler" effect. The Doppler effect occurs whenever a transmitted signal reflects off a target that has a motion relative to a transceiver. The resulting frequency shift is referred to as a "Doppler shift".
The transmit signal changes at regular intervals between three frequencies spaced 250 kHz apart. Two of the frequencies are used to generate range information as described therein, while a third frequency is used to determine Doppler closing rate and target selection. After substantial analog waveform detection, amplification, shaping, and gating, the information regarding range, closing rate, and target selection of a single target can be input to a microcontroller for digital processing.
The use of analog processing techniques is fast and allows real time processing. However, the cost of analog circuitry is typically much greater than the cost of digital circuitry. In addition, digital circuitry is more reliable and capable of higher precision and more complex processing than analog circuitry. Thus, the sooner the analog signal can be converted to a digital signal and handled by digital circuitry, the lower the cost, the greater the performance, and the higher the reliability of the system. Additionally, digital signal processing circuits are much less sensitive to temperature and manufacturing variations and interference from noise than are analog signal processing circuits. Furthermore, the use of analog signal processing techniques limits the number of features that can be added to a system since each new feature typically requires all new processing hardware. In contrast, many additional features can be added to a system in which digital signal processing is used to determine range and relative motion simply by adding or modifying software. Still further, in analog systems the level of sophistication that can be achieved is limited by the available hardware and the cost of such hardware.
Furthermore, in vehicular radar systems, only a small part of the reflected signal is returned to the antenna. Thus, target detection runs from very good to non-existent, even when a strongly reflecting target is present. Improving the ability to detect targets requires sophisticated signal processing and tracking algorithms. Under many circumstances, such sophisticated signal processing is the only means by which meaningful information can be attained. Without sophisticated information processing, it may be difficult to identify and interpret the reflected signal. This requirement for sophisticated processing makes digital signal manipulation especially advantageous.
Another means by which roadways are being made more safe is by recording operational information regarding drivers and vehicles during vehicle operation. A number of electronic devices exist that record data on various aspects of vehicle performance and/or environment information. Such devices have used magnetic tape and paper strips to record such information. These devices primarily function as trip recorders, storing information such as trip distance, trip time, miles per gallon consumed, and average speed.
A drawback of such devices is that magnetic tapes and paper strips are susceptible to the detrimental effects of heat and vibration commonly found in a vehicular environment. A further drawback is that prior art vehicular recording devices have not been used in conjunction with an automotive radar system to record such information as the closing rate (CR) between the recording vehicle and other vehicles located by the vehicle's radar system, the distance (D) between the recording vehicle and other vehicles, vehicle speed (VS), and such vehicle performance and environment information as braking pressure, vehicle acceleration or deceleration in one or more dimensions, rate of turning of the vehicle, steering angle, hazard levels determined from a radar system processor, detected vehicle direction, and cruise control status, to name a few.
Further, it is believed that such automotive recording devices have not been used to record information to be used for accident reconstruction. Most commercial aircraft and some private aircraft are equipped with an event recording device commonly called a "black box". This device records pertinent data from the aircraft's major subsystems as the aircraft is operating. If an accident occurs, the "black box" generally can be retrieved from the aircraft and the recorded information extracted to determine the status of subsystems of the aircraft just before the accident. Such information is then used to reconstruct the events leading up to the accident, and can help determine the cause of the accident. Black box recording devices have proven invaluable in aircraft accident reconstruction. However, this type of technology is quite expensive, and its use has been limited to more expensive vehicles such as aircraft. In addition, it is believed that all such devices operate using a cumbersome magnetic tape to record data. These devices also tend to be larger, heavier, consume more power, and cost more than would be acceptable for automotive use.
In the area of automobile accident reconstruction, an accident analyst determines how an accident most probably occurred by measuring, among other things, the length of skid marks, the extent of vehicle and nearby property damage, and the condition of the road at the time of the accident. This method of reconstructing accidents has been shown to be expensive and inaccurate at times. Accordingly, it would be desirable for automotive vehicles to have a system that would function as an event recording "black box". Such a system should record information relating to the vehicle and the environment around the vehicle prior to an accident. Such data should be readable after an accident for use in reconstructing the events leading up to the accident. An accident could then be reconstructed using real historical data, as opposed to post-accident estimated data.
In addition to recording data useful for accident reconstruction, it would also be desirable for such a device to record more standard vehicle performance, operational status, and/or environment data. In addition, it would be desirable that such a device be configurable for a driver's particular preferences, or to provide an authorization function that prohibits unauthorized personnel from driving the vehicle, and/or to provide a convenient means for upgrading system-wide software for an automotive electronic control system or an automotive radar system.
Accordingly, there is a need for an automotive event recording system. In addition, there is a need for an automotive radar system that converts signals received into digital form before processing of those signals. Furthermore, there is a need for a simplified system in which only two frequencies are broadcast and in which a larger portion of the transmit signal is useful. The present invention provides a system which accomplishes these desired objectives.
Still further, it would be desirable to have a method and apparatus which utilizes the information that is gathered by a radar system and other sensors, and the information that has been recorded during past trips and a present trip, to evaluate a driver's performance in real-time and under actual conditions. It would also be desirable for such a system to predict when a driver is near the point of being unfit to safely operate a vehicle and determine when the driver is actually unfit to safely operate a vehicle.
The present invention meets these needs.